1. Field of the invention
The present invention relates to a control valve assembly adapted to be used for supplying and discharging a pressurized oil to and from a single acting hydraulic cylinder, and more specifically to a control valve assembly of the type adapted to prevent a leakage of a pressurized oil between a valve member and a valve seat by employing a poppet valve as valve members to be inserted into a valve chamber.
2. Prior Art
The present invention resides in an improvement of a control valve assembly of the type described in Japanese Patent Publication No. 1989-31067 (referred to as the first conventional embodiment hereinafter) or in Japanese Laid Open Patent Publication 1983-170906 (referred to as the second conventional embodiment hereinafter).
These first and second conventional embodiments were previously proposed by the inventor of the present invention. The basic construction thereof is as follows as shown in FIG. 7 (for the first conventional embodiment) or in FIG. 8 (for the second conventional embodiment).
In a valve chamber 104, 204 of a valve assembly 101, 201 there are provided a pressure supply port P opened on the upper end side as the first end side thereof, a return port R opened on the lower end side as the second end side thereof and a working port A opened at a position out of both those ports P, R respectively.
A pressure supply valve seat 115, 215 is formed at the outer peripheral portion of the pressure supply port P, and a return valve seat 116, 216 is formed at the outer peripheral portion of the return port R. A check valve member 119, 219 is resiliently urged to the pressure supply valve seat 115, 215 by means of a check valve member closing spring 120, 220. A return valve member 122, 222 is resiliently urged to the return valve seat 116, 216 by means of a return valve member closing spring 130, 230.
A return operation means 137, 237 is disposed outside the lower end portion of the valve chamber 104, 204, and a valve opening member 143, 243 is disposed opposedly to the return valve member 122, 222 from the side of the return port R.
The aforementioned valve assembly 101, 201 operates as follows.
In the case that the return operation means 137, 237 is not operated, firstly the return valve member 122, 222 is brought into contact with the return valve seat 116, 216 for valve closing by means of a resultant force obtained from a resilient force of the return valve member closing spring 130, 230 and an interior pressure of the valve chamber 104, 204, and the pressurized oil within the pressure supply port P pushes and opens the check valve member 119, 219 so as to be supplied to the valve chamber 104, 204 and the working port A and to provide a pressure supplied condition for the valve assembly. Subsequently, when the interior pressure within the valve chamber 104, 204 reaches a predetermined pressure, the check valve member 119, 219 is brought into contact with the pressure supply valve seat 115, 215 for valve closing by means of a resilient force of the check valve member closing spring 120, 220 so as to provide a pressure keeping condition for the valve assembly.
Under the aforementioned pressure keeping condition, when the return operation means 137, 237 is operated, the valve opening member 143, 243 is advanced upward so that the return valve member 122, 222 can be pushed and opened by means of the leading end portion of the valve opening member 143, 243. Thereby, the pressurized oils within the working port A and the valve chamber 104, 204 are discharged to the return port R.
In the above-mentioned basic construction, the first and second conventional embodiments have the following construction for assembling the check valve member 119, 219 and the return valve member 122, 222 within the valve chamber 104, 204.